This invention relates to fluid jet drilling nozzles and methods for fluid jet drilling.
Although high velocity fluid jets have found a considerable number of applications in the cutting or scoring of various materials, the use of fluid jets for drilling in rock or other substances have received relatively little attention. One of the problems inherent in fluid jet drilling is that the fluid jets lose much of their cutting ability if the jet forming nozzle is too great a distance from the surface being cut. It is therefore necessary for a fluid jet drilling technique to be capable of drilling a hole of large enough diameter for the drilling nozzle to enter, so that the nozzle may be advanced into the hole as it is cut. Fluid jets, however, are of quite small diameter, typically 0.01 inches, and therefore at any one instant the jet can only cut against a very small area of the rock. A practical technique is therefore needed by which a small diameter fluid jet can cut a hole having a diameter much larger than the jet.